1. Field of the Invention
The present invention relates to an extraction device capable of capturing and retrieving objects from hollow bodies, and in particular, to a medical instrument for entrapping and removing an object from a body.
2. Background
Various instruments are known in the art for removing foreign objects from the body. For example, such instruments are used for removal of stones such as kidney stones, gall stones, and the like from various sites along the urinary tract of the patient's body. Retrieval devices are also widely used for removing foreign articles from the vascular system of a patient. In such a case, examples of the foreign articles include vena cava filters and parts of medical devices such as catheters, guide wires, cardiac leads, etc., which may break and become detached during medical procedures.
Some of these instruments employ a snare configured as a single distal loop which is positioned over a free end of the foreign body, and which is collapsed and tightened around the foreign body. One drawback to such a retrieval device is that the foreign object may be difficult to hook with the distal loop of the snare, which may require significant manipulation in order to capture the foreign object. Another drawback is that although the distal hook may capture the foreign object, retrieval of the foreign object may be difficult. This is because during retrieval of the foreign object the hook and the captured object are typically misaligned with the axis of the sheath, thereby hindering retraction of the hook and the foreign object into the sheath.